In the south refrigeration is probably the most challenging part of living off-grid on a budget. It is certainly possible to live without it – our ancestors did and we have – but it makes handling our milk and cheese much more productive. Our solar power system is very small, less than 300 watts, as is our budget so investing in more power and one of the refrigerators designed for off-grid use (the Sunfrosts or propane models) wasn’t an option. After some research we have found a way to have ample refrigerated space that will operate within the constraints of our small system – the converted chest freezer.
The process is simple. We purchased an external analog thermostat at a brewing supply store. Cost was about $75.
The freezer cord piggy-backs to the rear of the the thermostat cord. . .
And the thermostat probe is placed in the freezer. The freezer door has no trouble sealing around the thin probe wire. The thermostat is set to the desired temperature and when that temperature is reached it cuts all power to the freezer and restarts it when the threshold is exceeded. We run ours at 46 degrees.
We had to purchase a new inverter to run the system due to the startup wattage of the freezer. Our old inverter was 410 watts with a 750 watt surge which was too small. We continue to use it for our other, very small, power needs. The new inverter is 1000 watts with a 2000 watt surge and handles the freezer startup load with no problems. After startup the refrigerator pulls around 160 watts for about 10 minutes each hour in 90+ degree weather. This “costs” us 600 to 700 watts daily which is within the capacity of our system.
We use plastic bins to organize our food and place those requiring colder temperatures on the bottom. In the hottest weather we have found that placing several blankets over the lid helps insulate the unit.
The setup is much more energy efficient than a regular refrigerator for a couple of reasons. First, the cold air isn’t dumped out every time the lid is opened. In addition, a freezer is much better insulated than a refrigerator. An Energy Star freezer (ours isn’t) would probably run even more efficiently. We looked specifically for a manual defrost model with no light bulb. When we set up the project we found that our batteries were failing, which made the compressor run rough. A new set of batteries solved the problem. The refrigerator does produce quite a bit of condensation and requires wiping out periodically. Once a month works for us.